The present invention pertains to a rotary body, which is used to compensate the fanout in a printing press or is provided, still outside the printing press, for installation for the purpose of fanout compensation. The printing press is a machine that prints according to the wet method, preferably with the use of a moistening agent. Offset printing shall be mentioned here as an example in particular. The printing press may be a newspaper printing press for printing large newspaper runs. The web is preferably guided as an endless web through the machine and is wound off from a roll, i.e., the printing press is a web-fed printing press and especially preferably a web-fed rotary printing press in such an embodiment.
Changes occur in lateral expansion in printing presses because of the liquid having penetrated the web. This phenomenon, known as fanout, has the undesired consequence that the width of the web measured at right angles to the direction of conveying of the web changes between two printing gaps in which the web is printed on one after another. Even though the fanout phenomenon may be caused, in principle, by the ink that alone has penetrated, the fanout is significant in practice especially in the case of printing operating with moistening agent because of the moistening of the web which is associated with it. The web moistened in the upstream printing gap along the web swells on its way and becomes wider in the next printing gap of the two printing gaps, which is located downstream along the web. This leads to printer""s errors in the transverse direction of the web unless measures are taken to compensate the change in width.
EP 1 101 721 A1 shows devices for compensating the fanout for the web-fed rotary printing, with which the web is deformed in a wave-shaped pattern at right angles to its direction of conveying before it runs into a next printing gap, in which it is printed on. The width of the web is corrected, i.e., compensated in such a way that it is adapted in advance to the change in width that is to be expected based on the fanout. Since the extent of the change in width that can be attributed to the fanout may change from one run to the next and even within one run when the paper is changed because of different paper grades, EP 1 101 721 A1 also describes, among other things, adjustable fanout compensators, with which the amplitude of the imposed wave shape of the web can be changed in a specific manner. An increase in the amplitude brings about a reduction in the width of the web. The described embodiments of adjustable fanout compensators are formed by a plurality of bodies each, which are arranged along an axis of rotation of the compensator in question alternatingly next to one another and form, corresponding to the desired wave shape of the web, radially projecting head sections and setback foot sections, which are adjustable in relation to one another in order to adapt the extent of the projection and setback of the sections in adaptation to the extent of the change in width that can be attributed to the fanout. However, the prior-art devices, which proved to be successful per se, are complicated and therefore lead to a comparatively high initial cost.
Furthermore, EP 1 101 721 A1 also discloses a fanout compensator that is designed as a rotary body in one piece. This comparatively simple compensator has proved to be successful in practice. However, adaptation to changing run conditions is possible with such a compensator only by keeping ready a plurality of different rotary bodies, which are stored in the printing press in, e.g., a changing frame and can be introduced into or removed from the print run by an adjusting movement of the changing frame.
The object of the present invention is to also make possible the compensation of a change in the width of a web to be printed on, which change can be attributed to the fanout in adaptation to different run conditions in a simple and inexpensive manner.
The present invention pertains to a rotary body, which is provided for compensating the fanout in a printing press or is already installed in the press in order to guide a web to be printed on, which wraps around the rotary body. The wrapping angle should be at least 3xc2x0. However, a wrapping angle of 5xc2x0 or more, e.g., 10xc2x0, is preferred. The wrapping angle may reach up to 180xc2x0. The rotary body is intended for being mounted rotatably around an axis of rotation, which extends through the rotary body. Along the axis of rotation, the rotary body forms head sections and foot sections alternatingly next to each other. The surface sections formed by the head and foot sections form the jacket surface of the rotary body. The head sections project over the foot sections radially to the axis of rotation by height differences. Even though the wave contour thus obtained in the axial direction may, in principle, contain jumps, it is preferably continuous. It is especially preferably continuously differentiable and curved in the axial direction, insofar as this can be achieved with the manufacturing methods available in practice at an economically acceptable price. If arc sections with curvatures, which are different, or arc sections with straight axial sections meet, the wave contour may have kinks. Such kinks should be machined such that they have an obtuse angle or are even more preferably round.
According to the present invention, the head and foot sections are not rotatable in relation to one another around the axis of rotation because they are either fitted together and connected to one another in a torsion-proof manner, or they are formed by the rotary body in one piece. Even though examples of such rotary bodies with a wave profile have been known, in principle, from EP 1 101 721 A1, the present invention combines the feature of the torsion-proof connection or, more preferably, the one-piece design with the advantage of adjustability because the radial height differences existing between the head sections and the foot sections increase from minima, which they have along a first straight line offset in parallel to the axis of rotation, to maxima in the circumferential direction around the axis of rotation. The height differences preferably increase monotonically in the circumferential direction. The height differences show the maxima along a second straight line offset in parallel to the axis of rotation. The first straight line and the second straight line are preferably tangents to all head sections, namely, if all head sections have the same radial height in relation to the axis of rotation. If this is not the case, the two straight lines are the tangents to the head section projecting the farthest or to the group of head sections projecting the farthest. A rotary movement around the axis of rotation that is uniform for the entire rotary body is sufficient for the adjustment of the rotary body.
In one preferred embodiment, the height differences assume their maxima along a single straight line. However, it is also possible, in principle, for the maxima to be assumed not only along exactly one straight line, but in an area extending over a certain arc length around the axis of rotation. This may, in principle, also apply in relation to the minima.
The rotary body according to the present invention can be mounted in the printing press in a simple manner and can be mounted rotatably in the same manner as other rotary bodies of the printing press, e.g., deflecting rollers. The assembly of parts that can be adjusted in relation to one another, as in the prior-art, adjustable fanout compensators, is not necessary.
Even though the one-piece design over the entire width of the web is clearly preferred, a fanout compensator is also advantageous that is formed by arranging a few one-piece rotary bodies, e.g., two rotary bodies, next to each other along their common axis of rotation. Compared to a rotary body from individual bodies assembled in a torsion-proof manner, which form a head section or foot section each and are likewise still the subject of the present invention, the assembly from optionally two or three rotary bodies with a wave profile is markedly simpler.
The radial height differences by which the head sections project over the foot sections increase monotonically from their minima in the circumferential direction preferably in both directions of rotation. More preferably, they increase continuously in both directions of rotation. It is most favorable if they increase uninterruptedly continuously in both directions of rotation, which mathematically means that the radial height differences plotted as a function of the angle of rotation are continuously differentiable functions of the angle of rotation. The height differences increase especially preferably linearly or at least approximately linearly with the angle of rotation.
Corresponding to preferred embodiments, the surface sections formed by the head sections have the same shape. The equality of the shape of the surfaces is also preferred for the foot sections. The surfaces of the head sections and/or the surfaces of the foot sections should form circles in any cross section along the axis of rotation. However, other surfaces, which are round around the axis of rotation everywhere, are also advantageous. Should kinks develop in the circumferential direction around the axis of rotation due to a manufacturing process, the round arc pieces meeting each other at the kinks should join each other possibly at obtuse angles, which should equal at least 120xc2x0. However, it is more advantageous to avoid kinks or even jumps in the circumferential direction even for the rotary bodies obtained according to such manufacturing methods by making the kinks or even jumps round by a suitable finishing, e.g., grinding and polishing.
A fanout compensator, which is arranged at a suitable site on the path of the web between two printing gaps, comprises the rotary body according to the present invention, a rotary mount, in which the rotary body is mounted rotatably around its axis of rotation, and a control or regulating device with a final control element for generating a rotary adjusting movement of the rotary body around its axis of rotation. The rotary adjusting movement is a rotary movement, by which the rotary body is rotated around its axis of rotation from a first angle of rotation position, in which the web is wrapped around the rotary body symmetrically in relation to a first wave contour, into another, second angle of rotation position, in which the web is wrapped around the rotary body symmetrically in relation to a differently shaped, second wave contour. One of the wave contours may be a straight line, namely, if the minimal height differences are xe2x80x9czero.xe2x80x9d
In one variant, the rotary body has fluid channels, which form a plurality of opening sites on its surface. The fluid channels are used in an especially advantageous fanout compensation process to admit fluid to the surface of the rotary body. The fluid is preferably a pressurized gas and may be especially compressed air. The fluid forms a fluid gap, a kind of fluid cushion, in the area wrapped by the web between the surface of the rotary body and the underside of the web facing it. The fluid gap prevents ink that adheres to the underside of the web and is not yet dried from being able to be transferred to the rotary body, which could lead to disturbances. Furthermore, the friction is reduced.
The fluid channels may be designed as holes and extend from their opening sites on the surface through the rotary body radially inwardly into one cavity or optionally into a plurality of cavities, by which they are connected to a fluid source. Such holes may be especially straight and unbranched.
Each of the fluid channels may be separated from each of the other fluid channels and form a single opening site each. However, the fluid channels or some of the fluid channels may also be branched off toward the outer jacket surface and form a plurality of opening sites each there. Thus, providing the rotary body as a whole or, in case of the design as a hollow body, at least its ring section forming the fluid channels with a porosity sufficient for guiding the fluid corresponds to a likewise preferred embodiment. The porosity is preferably open porosity, so that the pore channels formed by the material form the fluid channels. The original shaping by compression molding a powder, preferably a metal powder, with subsequent or simultaneous sintering of the molding is especially suitable for forming a porous rotary body or rotary body ring section. Fluid channels formed in two manners may also occur in the same rotary body, i.e., both pore channels and fluid channels prepared subsequently may be present in the same rotary body.
The opening sites of the fluid channels may be arranged in a uniformly distributed manner in the axial direction and in the circumferential direction over the surface of the rotary body. However, the density of the opening sites per unit area of the surface may vary periodically with the period of the head and foot sections in the axial direction while the distribution is preferably uniform in the circumferential direction. Thus, the surface density of the opening sites may be greater in the surface sections formed by the head sections than in the surface sections formed by the foot sections in order to compensate axial flows from the head sections into the foot sections.
The rotary body may be formed in the original shaping process in one piece in the shape according to the present invention or in a plurality of pieces, which are connected to one another in a torsion-proof manner, e.g., by the aforementioned compression molding and sintering of a powdered starting material. The starting material is preferably a powder of a metal or metal alloy, but may also be a powdered or granulated plastic, instead. If the rotary body is a plastic body, it is possible to shape this rotary body as an injection-molded body according to the injection molding process, so that it is obtained as an injection-molded body.
Especially shaping, e.g., drop-forging, may be considered for use as the manufacturing process to obtain a preferably continuously differentiable, three-dimensional wave shape, which is ideally round everywhere, in the case of a metallic rotary body.
In another, especially simple manufacturing process, a rotary body, which is rotationally symmetrical in relation to a single longitudinal symmetry axis, is formed in a first step. The jacket surface of such a one-piece starting body may have especially a regular wave shape with foot sections that form identical surface sections each, and with head sections that likewise form identical surface sections. The rotary body according to the present invention is obtained from the starting body by machining with a tool. The tool may be, e.g., a milling head, a linear roughing, grinding and polishing tool or preferably a turning tool. During the removal of material, the starting body and the tool perform a rotary movement in relation to one another around a machining axis that is eccentric to the longitudinal symmetry axis of the starting body, i.e., is offset in parallel. The tool may be rotated around the stationary starting body, or both the starting body and the tool may be rotated around the machining axis in relation to one another. The starting body may likewise be driven to perform a rotary movement around the machining axis for the material-removing machining, while the tool does not perform any rotary movement in relation to a frame of the machine tool in which the starting body is clamped. The radial distance between the tool and the machining axis is reduced during the relative rotary movement for the material-removing machining. This advantageously takes place due to the tool being moved radially in a straight line toward the machining axis. The distance is reduced until the tool has reached the first straight line along which the radial height differences between the foot sections and the head sections are xe2x80x9czero.xe2x80x9d An oversize, which may be left after the removal of material and is then subsequently removed by fine surface finishing, shall be ignored here.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.